This transition tracks changes to the visibility of target views in the
start and end scenes and moves views in or out from one of the edges of the
scene.

A Transition holds information about animations that will be run on its
targets during a scene change. Subclasses of this abstract class may
choreograph several child transitions (TransitionSet or they may
perform custom animations themselves. Any Transition has two main jobs:
(1) capture property values, and (2) play animations based on changes to
captured property values. A custom transition knows what property values
on View objects are of interest to it, and also knows how to animate
changes to those values. For example, the Fade transition tracks
changes to visibility-related properties and is able to construct and run
animations that fade items in or out based on changes to those properties.

Note: Transitions may not work correctly with either SurfaceView
or TextureView, due to the way that these views are displayed
on the screen. For SurfaceView, the problem is that the view is updated from
a non-UI thread, so changes to the view due to transitions (such as moving
and resizing the view) may be out of sync with the display inside those bounds.
TextureView is more compatible with transitions in general, but some
specific transitions (such as Fade) may not be compatible
with TextureView because they rely on ViewOverlay
functionality, which does not currently work with TextureView.

Transitions can be declared in XML resource files inside the res/transition
directory. Transition resources consist of a tag name for one of the Transition
subclasses along with attributes to define some of the attributes of that transition.
For example, here is a minimal resource file that declares a ChangeBounds
transition:

<changeBounds/>

Note that attributes for the transition are not required, just as they are
optional when declared in code; Transitions created from XML resources will use
the same defaults as their code-created equivalents. Here is a slightly more
elaborate example which declares a TransitionSet transition with
ChangeBounds and Fade child transitions:

In this example, the transitionOrdering attribute is used on the TransitionSet
object to change from the default TransitionSet.ORDERING_TOGETHER behavior
to be TransitionSet.ORDERING_SEQUENTIAL instead. Also, the Fade
transition uses a fadingMode of Fade.OUT instead of the default
out-in behavior. Finally, note the use of the targets sub-tag, which
takes a set of {code target} tags, each of which lists a specific targetId which
this transition acts upon. Use of targets is optional, but can be used to either limit the time
spent checking attributes on unchanging views, or limiting the types of animations run on
specific views. In this case, we know that only the grayscaleContainer will be
disappearing, so we choose to limit the Fade transition to only that view.

MATCH_NAME

Public constructors

Transition

public Transition ()

Constructs a Transition object with no target objects. A transition with
no targets defaults to running on all target objects in the scene hierarchy
(if the transition is not contained in a TransitionSet), or all target
objects passed down from its parent (if it is in a TransitionSet).

Transition

Perform inflation from XML and apply a class-specific base style from a
theme attribute or style resource. This constructor of Transition allows
subclasses to use their own base style when they are inflating.

Parameters

context

Context: The Context the transition is running in, through which it can
access the current theme, resources, etc.

attrs

AttributeSet: The attributes of the XML tag that is inflating the transition.

addTarget

Sets the target view instances that this Transition is interested in
animating. By default, there are no targets, and a Transition will
listen for changes on every view in the hierarchy below the sceneRoot
of the Scene being transitioned into. Setting targets constrains
the Transition to only listen for, and act on, these views.
All other views will be ignored.

The target list is like the targetId
list except this list specifies the actual View instances, not the ids
of the views. This is an important distinction when scene changes involve
view hierarchies which have been inflated separately; different views may
share the same id but not actually be the same instance. If the transition
should treat those views as the same, then addTarget(int) should be used
instead of addTarget(View). If, on the other hand, scene changes involve
changes all within the same view hierarchy, among views which do not
necessarily have ids set on them, then the target list of views may be more
convenient.

addTarget

Adds the id of a target view that this Transition is interested in
animating. By default, there are no targetIds, and a Transition will
listen for changes on every view in the hierarchy below the sceneRoot
of the Scene being transitioned into. Setting targetIds constrains
the Transition to only listen for, and act on, views with these IDs.
Views with different IDs, or no IDs whatsoever, will be ignored.

Note that using ids to specify targets implies that ids should be unique
within the view hierarchy underneath the scene root.

addTarget

Adds the Class of a target view that this Transition is interested in
animating. By default, there are no targetTypes, and a Transition will
listen for changes on every view in the hierarchy below the sceneRoot
of the Scene being transitioned into. Setting targetTypes constrains
the Transition to only listen for, and act on, views with these classes.
Views with different classes will be ignored.

Note that any View that can be cast to targetType will be included, so
if targetType is View.class, all Views will be included.

The Transition to which the target class was added.
Returning the same object makes it easier to chain calls during
construction, such as
transitionSet.addTransitions(new Fade()).addTarget(ImageView.class);

addTarget

Adds the transitionName of a target view that this Transition is interested in
animating. By default, there are no targetNames, and a Transition will
listen for changes on every view in the hierarchy below the sceneRoot
of the Scene being transitioned into. Setting targetNames constrains
the Transition to only listen for, and act on, views with these transitionNames.
Views with different transitionNames, or no transitionName whatsoever, will be ignored.

The Transition to which the target transitionName is added.
Returning the same object makes it easier to chain calls during
construction, such as
transitionSet.addTransitions(new Fade()).addTarget(someName);

Subclasses must implement this method. The method should only be called by the
transition system; it is not intended to be called from external classes.

Parameters

transitionValues

TransitionValues: The holder for any values that the Transition
wishes to store. Values are stored in the values field
of this TransitionValues object and are keyed from
a String value. For example, to store a view's rotation value,
a transition might call
transitionValues.values.put("appname:transitionname:rotation",
view.getRotation()). The target view will already be stored
in
the transitionValues structure when this method is called.

Subclasses must implement this method. The method should only be called by the
transition system; it is not intended to be called from external classes.

Parameters

transitionValues

TransitionValues: The holder for any values that the Transition
wishes to store. Values are stored in the values field
of this TransitionValues object and are keyed from
a String value. For example, to store a view's rotation value,
a transition might call
transitionValues.values.put("appname:transitionname:rotation",
view.getRotation()). The target view will already be stored
in
the transitionValues structure when this method is called.

clone

createAnimator

This method creates an animation that will be run for this transition
given the information in the startValues and endValues structures captured
earlier for the start and end scenes. Subclasses of Transition should override
this method. The method should only be called by the transition system; it is
not intended to be called from external classes.

This method is called by the transition's parent (all the way up to the
topmost Transition in the hierarchy) with the sceneRoot and start/end
values that the transition may need to set up initial target values
and construct an appropriate animation. For example, if an overall
Transition is a TransitionSet consisting of several
child transitions in sequence, then some of the child transitions may
want to set initial values on target views prior to the overall
Transition commencing, to put them in an appropriate state for the
delay between that start and the child Transition start time. For
example, a transition that fades an item in may wish to set the starting
alpha value to 0, to avoid it blinking in prior to the transition
actually starting the animation. This is necessary because the scene
change that triggers the Transition will automatically set the end-scene
on all target views, so a Transition that wants to animate from a
different value should set that value prior to returning from this method.

Additionally, a Transition can perform logic to determine whether
the transition needs to run on the given target and start/end values.
For example, a transition that resizes objects on the screen may wish
to avoid running for views which are not present in either the start
or end scenes.

If there is an animator created and returned from this method, the
transition mechanism will apply any applicable duration, startDelay,
and interpolator to that animation and start it. A return value of
null indicates that no animation should run. The default
implementation returns null.

The method is called for every applicable target object, which is
stored in the TransitionValues.view field.

Parameters

sceneRoot

ViewGroup: The root of the transition hierarchy.

startValues

TransitionValues: The values for a specific target in the start scene.

excludeChildren

Whether to add the children of the given id to the list of targets to exclude
from this transition. The exclude parameter specifies whether
the children of the target should be added to or removed from the excluded list.
Excluding children in this way provides a simple mechanism for excluding all
children of specific targets, rather than individually excluding each
child individually.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded either by their
id, or by their instance reference, or by the Class of that view
(eg, Spinner).

Parameters

targetId

int: The id of a target whose children should be ignored when running
this transition.

exclude

boolean: Whether to add the target to or remove the target from the
current list of excluded-child targets.

excludeChildren

Whether to add the given type to the list of types whose children should
be excluded from this transition. The exclude parameter
specifies whether the target type should be added to or removed from
the excluded list.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded either by their
id, or by their instance reference, or by the Class of that view
(eg, Spinner).

Parameters

type

Class: The type to ignore when running this transition.

exclude

boolean: Whether to add the target type to or remove it from the
current list of excluded target types.

excludeChildren

Whether to add the children of given target to the list of target children
to exclude from this transition. The exclude parameter specifies
whether the target should be added to or removed from the excluded list.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded either by their
id, or by their instance reference, or by the Class of that view
(eg, Spinner).

Parameters

target

View: The target to ignore when running this transition.

exclude

boolean: Whether to add the target to or remove the target from the
current list of excluded targets.

excludeTarget

Whether to add the given target to the list of targets to exclude from this
transition. The exclude parameter specifies whether the target
should be added to or removed from the excluded list.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded either by their
id, or by their instance reference, or by the Class of that view
(eg, Spinner).

Parameters

target

View: The target to ignore when running this transition.

exclude

boolean: Whether to add the target to or remove the target from the
current list of excluded targets.

excludeTarget

Whether to add the given type to the list of types to exclude from this
transition. The exclude parameter specifies whether the target
type should be added to or removed from the excluded list.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded either by their
id, or by their instance reference, or by the Class of that view
(eg, Spinner).

Parameters

type

Class: The type to ignore when running this transition.

exclude

boolean: Whether to add the target type to or remove it from the
current list of excluded target types.

excludeTarget

Whether to add the given transitionName to the list of target transitionNames to exclude
from this transition. The exclude parameter specifies whether the target
should be added to or removed from the excluded list.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded by their
id, their instance reference, their transitionName, or by the Class of that view
(eg, Spinner).

Parameters

targetName

String: The name of a target to ignore when running this transition.

exclude

boolean: Whether to add the target to or remove the target from the
current list of excluded targets.

excludeTarget

Whether to add the given id to the list of target ids to exclude from this
transition. The exclude parameter specifies whether the target
should be added to or removed from the excluded list.

Excluding targets is a general mechanism for allowing transitions to run on
a view hierarchy while skipping target views that should not be part of
the transition. For example, you may want to avoid animating children
of a specific ListView or Spinner. Views can be excluded either by their
id, or by their instance reference, or by the Class of that view
(eg, Spinner).

Parameters

targetId

int: The id of a target to ignore when running this transition.

exclude

boolean: Whether to add the target to or remove the target from the
current list of excluded targets.

getEpicenterCallback

Returns the callback used to find the epicenter of the Transition.
Transitions like Explode use a point or Rect to orient
the direction of travel. This is called the epicenter of the Transition and is
typically centered on a touched View. The
Transition.EpicenterCallback allows a Transition to
dynamically retrieve the epicenter during a Transition.

The interpolator set on this transition, if one has been set, otherwise
returns null.

getName

public String getName ()

Returns the name of this Transition. This name is used internally to distinguish
between different transitions to determine when interrupting transitions overlap.
For example, a ChangeBounds running on the same target view as another ChangeBounds
should determine whether the old transition is animating to different end values
and should be canceled in favor of the new transition.

By default, a Transition's name is simply the value of Class.getName(),
but subclasses are free to override and return something different.

getPropagation

Returns the TransitionPropagation used to calculate Animator
start
delays.
When a Transition affects several Views like Explode or
Slide, there may be a desire to have a "wave-front" effect
such that the Animator start delay depends on position of the View. The
TransitionPropagation specifies how the start delays are calculated.

getStartDelay

Returns the startDelay set on this transition. If no startDelay has been set,
the returned value will be negative, indicating that resulting animators will
retain their own startDelays.

Returns

long

The startDelay set on this transition, in milliseconds, if one has
been set, otherwise returns a negative number.

getTargetIds

public List<Integer> getTargetIds ()

Returns the array of target IDs that this transition limits itself to
tracking and animating. If the array is null for both this method and
getTargets(), then this transition is
not limited to specific views, and will handle changes to any views
in the hierarchy of a scene change.

Returns

List<Integer>

the list of target IDs

getTargetNames

public List<String> getTargetNames ()

Returns the list of target transitionNames that this transition limits itself to
tracking and animating. If the list is null or empty for
getTargetIds(), getTargets(), getTargetNames(), and
getTargetTypes() then this transition is
not limited to specific views, and will handle changes to any views
in the hierarchy of a scene change.

Returns

List<String>

the list of target transitionNames

getTargetTypes

public List<Class> getTargetTypes ()

Returns the list of target transitionNames that this transition limits itself to
tracking and animating. If the list is null or empty for
getTargetIds(), getTargets(), getTargetNames(), and
getTargetTypes() then this transition is
not limited to specific views, and will handle changes to any views
in the hierarchy of a scene change.

Returns

List<Class>

the list of target Types

getTargets

Returns the array of target views that this transition limits itself to
tracking and animating. If the array is null for both this method and
getTargetIds(), then this transition is
not limited to specific views, and will handle changes to any views
in the hierarchy of a scene change.

getTransitionProperties

public String[] getTransitionProperties ()

Returns the set of property names used stored in the TransitionValues
object passed into captureStartValues(TransitionValues) that
this transition cares about for the purposes of canceling overlapping animations.
When any transition is started on a given scene root, all transitions
currently running on that same scene root are checked to see whether the
properties on which they based their animations agree with the end values of
the same properties in the new transition. If the end values are not equal,
then the old animation is canceled since the new transition will start a new
animation to these new values. If the values are equal, the old animation is
allowed to continue and no new animation is started for that transition.

A transition does not need to override this method. However, not doing so
will mean that the cancellation logic outlined in the previous paragraph
will be skipped for that transition, possibly leading to artifacts as
old transitions and new transitions on the same targets run in parallel,
animating views toward potentially different end values.

Returns

String[]

An array of property names as described in the class documentation for
TransitionValues. The default implementation returns null.

getTransitionValues

This method can be called by transitions to get the TransitionValues for
any particular view during the transition-playing process. This might be
necessary, for example, to query the before/after state of related views
for a given transition.

The Transition from which the targetId is removed.
Returning the same object makes it easier to chain calls during
construction, such as
transitionSet.addTransitions(new Fade()).removeTargetId(someId);

Transition The Transition from which the target is removed.
Returning the same object makes it easier to chain calls during
construction, such as
transitionSet.addTransitions(new Fade()).removeTarget(someView);

The Transition from which the targetName is removed.
Returning the same object makes it easier to chain calls during
construction, such as
transitionSet.addTransitions(new Fade()).removeTargetName(someName);

Transition The Transition from which the target is removed.
Returning the same object makes it easier to chain calls during
construction, such as
transitionSet.addTransitions(new Fade()).removeTarget(someType);

setDuration

Sets the duration of this transition. By default, there is no duration
(indicated by a negative number), which means that the Animator created by
the transition will have its own specified duration. If the duration of a
Transition is set, that duration will override the Animator duration.

setEpicenterCallback

Sets the callback to use to find the epicenter of a Transition. A null value indicates
that there is no epicenter in the Transition and onGetEpicenter() will return null.
Transitions like Explode use a point or Rect to orient
the direction of travel. This is called the epicenter of the Transition and is
typically centered on a touched View. The
Transition.EpicenterCallback allows a Transition to
dynamically retrieve the epicenter during a Transition.

Parameters

epicenterCallback

Transition.EpicenterCallback: The callback to use to find the epicenter of the Transition.

setInterpolator

Sets the interpolator of this transition. By default, the interpolator
is null, which means that the Animator created by the transition
will have its own specified interpolator. If the interpolator of a
Transition is set, that interpolator will override the Animator interpolator.

setMatchOrder

public void setMatchOrder (int... matches)

Sets the order in which Transition matches View start and end values.

The default behavior is to match first by View.getTransitionName(),
then by View instance, then by View.getId() and finally
by its item ID if it is in a direct child of ListView. The caller can
choose to have only some or all of the values of MATCH_INSTANCE,
MATCH_NAME, MATCH_ITEM_ID, and MATCH_ID. Only
the match algorithms supplied will be used to determine whether Views are the
the same in both the start and end Scene. Views that do not match will be considered
as entering or leaving the Scene.

setPathMotion

Transitions such as ChangeBounds move Views, typically
in a straight path between the start and end positions. Applications that desire to
have these motions move in a curve can change how Views interpolate in two dimensions
by extending PathMotion and implementing
PathMotion.getPath(float, float, float, float).

Parameters

pathMotion

PathMotion: Algorithm object to use for determining how to interpolate in two
dimensions. If null, a straight-path algorithm will be used.

setPropagation

Sets the method for determining Animator start delays.
When a Transition affects several Views like Explode or
Slide, there may be a desire to have a "wave-front" effect
such that the Animator start delay depends on position of the View. The
TransitionPropagation specifies how the start delays are calculated.

Parameters

transitionPropagation

TransitionPropagation: The class used to determine the start delay of
Animators created by this Transition. A null value
indicates that no delay should be used.

setStartDelay

Sets the startDelay of this transition. By default, there is no delay
(indicated by a negative number), which means that the Animator created by
the transition will have its own specified startDelay. If the delay of a
Transition is set, that delay will override the Animator delay.